Assig-nob of one-foubth



(No Model.) 2 Sheets-Sheet 1. H. GLDVER.

ISOMBTER 0R DYNAMIC SECTUR.

No. 303,928. Patented Aug. 19, 1884.

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,Wllhzressesr l ,Imerzfors 5% iq/ff., awww? 1 2 Sheets--Sheet 2.

(No Mgdel.)

H. GLOVER.

ISOMBTER 0R DYNAMIC SECTOR.

Jggllatented Aug. 1Q, 1884,

Cri

UNiTen STATES PATENT Oriiieeo ll'lllNllY GLOVER, (JF BlitOOU/YN, NEW'YORK., ASSIGNOR (,)F

T() HLLEN BEBEE, 0F SAME PLACE.

isop/eren ori oYNAivno sEoToR.

SPECIFICATION forming part of Letters P Alllllilnlion llloil July ltl`lfill,

To (LZ whom it may concern:

ie it known tlizit l, HENRY (ilmivlli, :t eiti- :con of tlie UnitedStates, and :t resident oi' 'iroolilyin in the county ol" Kings andSlate of YouY l'oilc, lieve ininfnted oei-tuin new and usefullniproi'enienis in lsonieters or llynaniie Sectors, ol ii'hieli thefollowing is :i speeilieation.

Ny invention, ii'liieli l terni an isonieter or dynaniie setter,"lrelates to :in improvement in llintelass ofpliilosopliiealinstruiiienlis ii'liieli :ire terined 'lioiissiiles,"7 and isapplic-,able to fill sueli apparatuses, in their various forms, where apivoted niagnetneedle is employed to r graphically indicate the magneticineridizin, wliieli passes through the center o tlie point ofobservation, and ii'liioh serves es the basis for furthernianipulationssueh as locating the true nieridian, as Well es itsrespective inagiietie meridian, to properly deliiie the latitude of anygiven point,to observe the exact amount of loool disturbances whichaffect the magnetic needle, as on board of :in ,iron ship, and for otherpurposes, hereinafter more i" ull y deserilied. As is well known, themagnetic meridian difiers from the true meridian by assuming daily a,different position, increasing or deer-easing either to the ezist orwest el the true meridian, and producing constantly*different bearingsat the various points of observations, `rliieli neeesstatesaearef ul ond protraeted correction by calculating suoli difference and bringing theresultto beer on the different observations. It is, furthermore, wellunderstood tliat'loeal 'attractions of various known endhidd en ceriseswill seriously interfere with arriving et any trueend efficient result,and tl'ieiiiaiiy preoau` tions taken to secure to the in ariner scompass, espeo lly :in iron shipls, o uiiiiorni aetion to beeoineunziiieeted by any loeal disturbances, and solely subject to thedelieetion el' the magnetie meridian, have not proven su'llieient toi-ieour`e at all times, andat ell points, and :it eaehelienge ofthesliips eourse, 4a inalheiiiati eallyeorreet base el' errors.

Among other purposes, my invention is designed to remove thisobjectionable featlireof ooleulating for and with the errors, and is soarranged/and iiroportionedY that by simply noting tliedeieotioii of theneedle on a ver nier seele, after the instrument has been ed atent No.303,928, dated August 19,1884.

(No modell j usted, the exact aniennt ol' errors Caused by loeal disterbuinies, ehengeof the ships course,

or by other causes, iiill er degress and minutes.

In the :ioeoiiipanyiiig drawings,

i lliistrates in invention to illustrates the sinne in az longitudinulvertical seetion, and Fig. 2 sli ows au ordinary transit (fr ortlieodolite ln Fig. l, A. is the index-lever, radially to the pivot lrind earrying treiiiity the vernieiplaiiie I3.

provided with niy apparatus.

i'nlerunied of llie free needle l?, on its outwardly-extending exltigidly zittziehed to the instrument, find extending radiallyoutwardly, is the seetor seele G.

with Vernier S The latter is divided into degrees and tenths of a degreeto either side of the zero-point, eaeh of seid degrees 7o being equal toone thirtyseeond of the eirele upon which the Vernier-seele is formed.Each Whole division upon the Vernier-plate B is subdivided into elevenequal parts bearing a proportion of eleven to teu of the subdivisions 75ol the iferniensezile.

ln Fig. 2,

G illustrates al fixed needle or nifignetie lizir solidly attached tothe underside ot the niain when said fixed needle is in exact line with8o the free needle l plate, and in suoli position that and the arin A isadjusted to bring pointer K in line with the needle F,

tlie zero of the seales C sliown'in the drawings.

and B willeoinoide, as K is located in the'` een ter line upon theindeielever A,eud slight 8 5 n ly proj eoting zibove and beyond thenorth Yend of the free needleF whenever, the latter is brouglitsto point.iny this direction. dex K is iii suoli position upon the The inlever Athat it coincides with the fixed-needle when 9o the lever'd is inposition to bring the zero of the seele und the Vernier in eoineideiice.

the present ease the index K is upon the seine radial line with theIixed needle,

lutter is displaced with relation 95- f i to the zero on sealeS by auein ount equal to the obvious, the

diiieren ee in so that, es` is circumferential position between theindex und tlie'zero of the-scale when the vernier reading is zero. Tothe standard L may he nifyingglass scales. The

to facilitate the' reading on the fixed needle G will exert itsiiiattaehed a niagioof 2 :sonore llucnce upon the free needle and causethelatter to assume 'a nearly like direction whenever the instrument hasbeen partly revolved in azimuth. The earths magnetic meridian passingthrough the center oftliis instrument will also exert its influence uponthe free needle F and cause the same to delico-t to the right or left ofthe index K to such an extent as the point of observation and itsposition and bearing to the true meredian warrant. ln case now theindex-lever A is revolved to such an extent that its index K will'coincide with the north end of the free needle F, then the position ofthe Vernier-plate B ou the scale C will indicate in points thedifiercnee between the truc and magnetic meridian-that is, assumingthat-ille fixed needle represents the true meridian-then the difi'erence between the magnetic and truc meridian is shown by the arc ofdeflection between both viz., the free statical resisting-needle beingsubmitted to two opposing forces will assume, according to thewell-known law of forces, a diagonal direction to the resistanceoffered. lVhen the instrument is revolved on its own axis until theindex or zero-bar is due east and west, the deflection ofthe free needlefrom the zero-point will have diverged to its uttermost limits,.andwhether this angle of deflection be attributed to magnetic currents orother undefined causes, it increases and decreases with the earthstangential force, and uniformly with the latitude of the place ofobservation; but when the instrument is on the true meridian of theplane of observation, then there is a perfect coincidence of the freeneedle and the index-point, and a parallelism of the free and fixedneedle, and any divergence whatcvci of the instrument from the truemeridian, either by rotating the instrument in azimuth or by localdisturbances, will cause a corresponding deflection ofthe needle,consequent` ly, at any time or place independent of solar observation orlocal magnetic disturbances, a true meridional-point can be determinedby simply revolving the instrument in azimuth until the free needlecoincides with the zero or index point.

Any local disturbance which mightopcrate in part to deiiect thefrce'nccdle can be easily ascertained by placingr the instrument i nazimuth east and west, and then rotating theindex-lever asmany points asthe plan of observation warranrs. Should the north end of the freeneedle not coincide with the index I( on `the index-lever, then theamount of points which it is necessary to further rotate the latter willindicate-the erroneous deflection caused by local disturbances. Suchpoints reduced to degrees, minutes,` and seconds will serve as a base oferrors in the various manipulations for which this apparatus isemployed. As per illustration: The instrument being situated at a pointin New York city, and lplaced in azimuth to a `point coinciding with itslateral bearing-viz., forty degrees and forty minutes, the defiectiou olthe needle at this point being equal to 3.6 points, and the index beingsetto this scale, adeflecton of the freeneedle is still observed, which,measured ou the scale after the indes: is brought to a coincidence withthe end of the needle and new yindicating 6.8, shows 3.2 points, causedby local disturbances at this point.

Iu Fig. 3 o1 drawings a practical application to a surveying-transit isillustrated, in which M represents the graduated scale of theinstrument, serving` as simple azimuth in the operation of my apparatus,and N any wellllcnown device for adjusting the saine. F is the freeneedle; K, the index-point; A, the index-lever,- C, the vernicr-scale,and B its plate.

As all sui- Veys for measuring distances to determine local andgeographical boundaries, &c., depend upon the accuracy of finding a trucmeridian, and as experience has shown that in many geographicallocalities the local disturbances ot' the magnetic needle are sovariable that it is, with existing n1eans,very diicult to obtainperfectly satisfactory results, free from instrumental errors; hence myinvention, as applied to this class of apparatuses in correcting its ownerror, and independent of celestial observation, will give perfectly true results.

In applying my invention to nautical instruments its prime object willbe, aside of determining the varial ion ofthe truc from the inagneticmeridian, to correct the error caused by local disturbances, sodifficult to combat in iron ships. Although this error can be de-ktected by celestial observations and other similar ingeniousdevces,still certain atmospheric conditions-such as foggyweather,equip1nent, or cargo*will at times prevent the usage of the sameby causing the magnetic needle to diverge froin itsnorxnal direction tosuch an extent as to render the same entirely useless for the purpose olnavigation. Especially would this be the case when the navigatorshouldleave port and almost complete his voyage with constant thick andcloudy weather, and the ships compass,as his sole guide, beinginfluenced by the magnetic condition of the ships cargo. From the factthat the error varies i n amount by each change of the ships course, andevery changefroln a. vertical position bythe ship lying over, the errorwill increase or decrease with the larboard erstarboard angle'of theship, which makes a true solution of this problem of error verydifficult.

IOC

IIO

It is apparent that au instrument that will V indicate the error at anytime, so that the true course can be estimatedfor any distance, Will beespecially advantageous for this purpose.

The construction of the scale on the sector, with its appending Vernier,is asiollows: The division of 0 to 32 corresponds with the thirty-twopoints of the azimuth-scale in such a manner that the Vernier O to l1represents the thirty-second part of the circle. This partis dividedintjo eleven parts for the Vernier, and into'ten equal parts for thescale. Thus one that is,

point of are on the sector equals the thirtyseecnd part of the circle,which gives the velue ofelevcn degrees fifteen minutes to' eee-hpointwhile controlled. by the fixed or secondary needle, :i distance ofone point, :is observed on the sector of `1n`y isonieter, will drive efree needle 'of an ordinzn'yreompuss eleven degrees iiteen minutes. Eachunit or whole point on the sector being equivalent to eleven degreeslfifteen minutes, by subdividing each point into tenths we obtain foreach subdivision a. value equivelcnttc one degree seven minutes :md fiveseconds of the crdinztry zizimutlrscelel The relative length of thefreeswinging needle to the iixed needle is proportioned es eighteen is3o responds, the 'free-swinging needle, and :in

the force that drives the free needlc,'

index-levier adapted to be swung so that its.

index will coincide with the free-swinging needle, and provided withewarnienplate oi' other device for use with the fixed seele, as

end for the purpose described.

3.`T11e combination of tl ic fixed nee die pl need beneath end madeslightly shorter than the free needle, the sector :ind scale projectingfrom the cese, the indexzmn carrying; index K, and the Vernier-plete B,as und for the purpose described.

4. rihe combination, with the fixedjmd the free-swinging needle, of acurved scdle-piete, each division oi' which is equal to one thirtyseeondof the circle upon which it is formed, mid is subdivided into tenths,and :L Vernier, eleven of whose subdivisions :tre equal to tensubdivisions of 'the sceleplete.

- 5. The combination, substantially es de scribed, of u. freesWinging,`needle and a iixed needle, relatively proportioned as eighteen tosixteen, und both acting eoncentrietlly with the indembni' unid scale.

Signed et New York, yin the county of New York und State of New York,this 5th dey ol"` July, A. D. 1883.

l HENRY GLQVER. XVitnesses:

Tiros. TOOMEY, M. M. FRIEND.

